6,689 research outputs found
Optimisation of a multi-layered meta-partition for broadband low-frequency sound insulation
No full textAcoustic metamaterials, which are usually composed of periodic subwavelength unit cells, are known for their unique capabilities in controlling sound wave propagation. One application of such metamaterials is in using their resonant properties as a lightweight and compact solution to the problematic low frequency range from conventional sound insulation treatments. However, the resonant property of metamaterials only allows for a narrow stopband with superior sound insulation. This paper aims to achieve broadband sound transmission loss in the low frequency range by proposing a multi-layered partition encompassing different metamaterial types. An analytical model of the partition is derived by treating the metamaterial layers with effective material properties inferred from a homogenization method. By applying constraints on the metamaterial and partition properties, such as the overall mass and thickness of the partition, optimizations are then performed to maximize the sound transmission loss within a specific frequency band. A numerical model of the optimized partition is produced to validate the analytical mode
A numerical study of a vibro-acoustic metamaterial with an embedded Helmholtz Resonator
No full textIn the recent decades, acoustic metamaterials are emerging as a lightweight and compact solution to extraordinary low frequency sound insulation. However, many acoustic metamaterials only exhibit superior performance in a narrowband region compared to the mass law of a homogeneous material with equivalent mass, which strongly limits their applications. This paper introduces a multi-modal vibro-acoustic metamaterial that combines structural and acoustical resonances to extend the bandwidth of the metamaterial, using acoustical resonances to improve the performance without affecting the weight of the metamaterial. Firstly, an analytical model is used as a simple approach to understanding the structural and acoustic properties of this metamaterial. Then, numerical simulations based on the finite element method are used to investigate the coupling between the structural and acoustical resonance mechanisms of the metamaterial and their effect on the sound transmission loss of the metamaterial
A sensitivity study approach to improve the sound transmission loss performance of vibro-acoustic metamaterials with embedded Helmholtz resonators
No full textAcoustic "meta-partitions", which are composed of a partition with periodically attached resonators, exhibit an improved low-frequency sound insulation by introducing a frequency region of superior transmission loss (TL) that exceeds the mass-law TL of a homogeneous partition with equivalent mass. A common resonator design for meta-partitions is a cantilever-type vibro-acoustic metamaterial, which has a simple design for manufacturing and tuning the TL performance. However, this type of metamaterial only achieves a narrowband TL improvement and introduces a frequency band with a TL deficit at higher frequencies. To improve the TL performance of the partition without adding mass, a Helmholtz resonator can be embedded into the cantilever resonator. This work aims to provide a deeper understanding into the design process of meta-partitions with cantilever-Helmholtz resonators by presenting sensitivity study results on the TL improvement and bandwidth through various input design parameters to an analytical model of the meta-partition. The TL of the meta-partition is predicted using the transfer matrix method, where the partition is represented as an effective medium with frequency dependent mass density and bulk modulus. With this work, guidelines on selecting certain values for each parameter are recommended to maximise the performance of this novel meta-partition design
Multi-layer vibro-acoustic meta-partitions with embedded Helmholtz resonators
No full textConventional partitions used for sound insulation require additional mass or thickness to improve their low-frequency sound transmission loss performance. This contradicts modern engineering applications, which seek lightweight and compact noise treatment. Acoustic metamaterials, which are usually composed of periodically arranged subwavelength unit cells, have the capabilities to offer extraordinary low-frequency sound insulation while also being lightweight and compact. However, many acoustic metamaterials exhibit only superior performance in a narrow band region compared to a partition constructed from a homogeneous material with equivalent mass, which limits their commercial use. This paper introduces a double-layer meta-partition, consisting of arrays of a new vibro-acoustic metamaterial design. The proposed vibro-acoustic metamaterials contain embedded Helmholtz resonators, thus combining both structural and acoustical resonances to increase the transmission loss at low frequencies without adding mass. Finite-element simulations were carried out to predict the transmission loss performance of the meta-partition and to understand the underlying physics behind the transmission loss peaks and dips. The finite-element simulation results showed that the proposed meta-partition design increased the bandwidth of transmission loss improvement and reduced transmission loss dips caused by partition resonances, such as the mass-air-mass resonance. An experimental proof-of-concept study was performed under impedance tube conditions, testing the proposed metamaterial unit cell samples under different conditions compared to those simulated in the numerical model. Despite different conditions, the experimental results match well with the corresponding simulation results, verifying numerical results for the infinitely large meta-partition
Interview with Kenneth Sprunt
No full textKenneth Sprunt was born in Wilmington in 1920, the third son of James Lawrence Sprunt. The Sprunts have a long history in and around Wilimington. His grandfather was a cotton merchant in the area and his great-great Uncle is the man for whom James Sprunt Community College is named for as well as the author of Chronicles of the Lower Cape Fear. Mr. Kenneth Sprunt relates his family history both before his birth and after. He spent three years in the Coast Guard during WWII primarily working on anti-submarine warfare in small boats
Memorandum from Kenneth Iyeko
No full textMemorandum from Kenneth Iyeko regarding establishment and support of the Japanese American Citizens' League at incarceration camps operated by War Relocation Authority.Personal correspondence, organizational records, government documents, publications, and other papers created or collected by Joseph R. Goodman documenting the forced removal and incarceration of Japanese Americans during World War II, as well as organized resistance to incarceration. Included in the collection are records of the Japanese Young Men's Christian Association and the Japanese American Citizens' League in San Francisco, including papers of the Japanese YMCA's executive secretary Lincoln Kanai; Sakai family papers; Goodman's correspondence to and from Japanese American incarcerees, organizations opposing forced removal and incarceration of Japanese Americans, the War Relocation Authority, and others; publications, photographs, and ephemera from the Topaz Relocation Center, where Goodman taught high school; War Relocation Authority records and publications; and newspaper clippings, pamphlets, and reports about forced removal and incarceration created by various government, religious, and civic organizations, in California and nationwide
A Review by Kenneth Atkinson of Alexandria and Qumran: Back to the Beginning, by Kenneth Silver
No full textKenneth Silver (a.k.a. Kenneth A. K. Lönnqvist), is a historian and professional archaeologist, who has lived and worked for decades in the Near East. With extensive publications on Hellenistic and Roman archaeology, history, and numismatics, Silver is the director of a survey and mapping project in Northern Mesopotamia studying the border zone between the late Roman/ Byzantine Empires and Persia. Author of numerous publications on Qumran and related topics, Silver’s lengthy monograph proposes that the documents and type of library found at Qumran were based on models derived from Egypt. The main thesis of the volume is that Pythagorean philosophy is the core and basis for the beliefs reflected in the non-Biblical texts found at Qumran
Patterning of chorion proteins in the drosophila eggshell
No full textM.S.Includes bibliographical referencesby Kenneth Ki
The implications for ministry of the teachings of Kenneth Cracknell with special reference to former students
No full textTo be effective in ministry in the contemporary religious milieu, today's seminarians, tomorrow's church leaders, must receive more than a mere academic experience; they need practical experience as to how to function effectively within a socially diverse climate of faith. The author documents the long term impact of Kenneth Cracknell's attempts to nurture cross cultural understanding and cooperation within the seminary context. The intent of this exposition is to demonstrate that Kenneth Cracknell has purposefully created a tranformative environment using interfaith dialogue as an effective paradigm for informing today's diverse seminary population. To that end, opinions, reactions and musings of a dozen former students are documented and presented herein as models of appropriate conversation for interfaith dialogue
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